When Bitcoin was $100 then a $1 move in price was a 1% change.

When Bitcoin was $1000 then a $1 move in price was a 0.1% change.

If Bitcoin gets mass adoption then the price per Bitcoin could be $50,000 (assume $1 trillion market cap) or higher. At that point a $1 market movement would be a 0.002% change. To get the same 10% movement as at $100 would require a $5,000 market price swing which while possible is less likely.

It means a lot more money would have to be bought or sold to cause the same percent movement in price.

Bitcoin is already much less volatile today than it was in the past.